Figure 6.

Phenolic compounds in leaves of P. euphratica (red) and P. canescens (blue). Soluble (a) and non-soluble phenolic compounds (b) were determined as catechin equivalents; soluble (c) and non-soluble condensed tannins (d) were determined as extinction units per gram g of fresh weight (n = 5, mean ± SD). Data in (b) are expressed mg per g of cell wall material (CW). Significant differences between the two poplar species are indicated by * for P ≤ 0.05, ** for P ≤ 0.01 and ** for P ≤ 0.001.